1. Field of the Invention
The present invention relates to print-data generating apparatuses, print-data processing apparatuses, and print systems, and more particularly, to the technique suitable for use in printing information on a sheet of paper.
2. Description of the Related Art
When printing information on a sheet of paper, the information is generally printed directly on the sheet such that the information can be visually conveyed. To edit or change the information printed on the sheet or to add new information to the sheet, electronic editing may be required.
To satisfy such needs, the technique of embedding a method of accessing electronic data corresponding to information printed on a sheet of paper in the information printed on the sheet in the form of, for example, a uniform resource locator (URL) or a file path has been proposed in, for example, Japanese Patent Laid-Open No 2001-30587. In this method, however, obtaining the electronic data corresponding to the information printed on the sheet requires an environment that permits accessing the electronic data using the accessing method embedded in the information printed on the sheet.
To solve the above-mentioned problem, the technique of embedding electronic data corresponding to information printed on a sheet of paper as a reversibly convertible image (meaning that the original electronic data can be regenerated after a change by the reverse of the change) has been proposed in, for example, Japanese Patent Laid-Open No 7-64481. In the following description, this technique is referred to as a “watermarking scheme” if needed.
In this technique, given a method of extracting the electronic data from such a watermark image, a user can obtain the electronic data corresponding to the information printed on the sheet regardless of the environment. The electronic data can also be carried and distributed easily in the form of paper, which is an inexpensive medium. The technique of embedding the method of accessing the electronic data in the information printed on the sheet requires a management source to store the electronic data. In contrast, the watermarking scheme does not require the management source to store the electronic data. Because of these advantages, the watermarking scheme in which electronic data is embedded and used as a watermark in a sheet of paper would become more popular in the future.
The technique of printing the above-described watermark image has an advantage that a person reading the sheet (hereinafter referred to as a “reader”) can obtain the electronic data from the sheet. However, the technique does not have an advantage of paper in that the information is directly and visually presented to the reader. To overcome the disadvantage, content equivalent to that of an electronic file stored in the watermark image may be printed on the sheet in such a format that the reader can read. When the electronic data is contained on the sheet in these two ways, that is, being printed so as to be readable by the reader and being embedded as a watermark, the convenience of both the electronic file and the paper can be inherited. However, the risk of information leakage becomes higher in both ways. If the information may be personal information or the like that requires secrecy, measures must be taken to avoid information leakage while ensuring the convenience of handling information.
Information printed on a sheet of paper can directly stimulate the vision of a reader. However, such information printed on the sheet is difficult to edit. In contrast, an electronic file produces less visual impact on the reader than paper, but can be easily edited. Unless the electronic file is opened using an application program, the information will not be leaked to the outside.
In the case that the details of information printed on a sheet of paper include secret information shared in advance by a printing source and a user, the following cannot be implemented by known techniques. That is, it has been difficult to prevent secret information from leaking even in the case that a printed side of the sheet is presented to people other than the user, and to prevent the user from entering the secret information again when editing an electronic file obtained from the watermark.